1. Field of the Invention
This invention relates to a novel liquid crystalline compound and a liquid crystal composition containing the same. More particularly it relates to a liquid crystalline compound having an optically active group and a chiral liquid crystal composition containing the same.
2. Description of the Related Art
At present, TN (Twisted Nematic) display mode has been most broadly employed, but it is inferior in the aspect of the response rate to emissive type display elements such as electroluminescence, plasma display, etc.; hence various improvements in this aspect have been attempted, but a possibility of its improvement to a large extent does not seem to remain so much. Thus, various devices based on another principle in place of that of TN mode display elements have been attempted, and among these there is a display mode utilizing ferroelectric liquid crystals (N. A. Clark et al; Applied Phys. lett., 36, 899 (1980)). This mode utilizes ferroelectric liquid crystal chiral smectic C phase (hereinafter abbreviated to SC* phase) or other smectic phases such as SH* phase, SF* phase, SG* phase, etc., and has the following three superior specific features as compared with TN display mode:
a first specific feature consists in that the mode affords a very high response rate, which amounts to 100 times those of TN mode display elements;
a second specific feature consists in that the mode affords a memory effect so that multiplex drive becomes easy in addition to the above-mentioned high rate response properties; and
a third specific feature consists in that it is possible to more easily obtain the gray scale than with a TN display mode only by adjusting an inverting time of polarity so that the mode has been considered to be suitable for graphic display.
However, in spite of the fact that the mode has the above-mentioned superior specific features, currently known ferroelectric liquid crystals and compositions have not yet afforded fully satisfactory results in the aspect of the response rate; hence the mode appears to have somewhat come to a deadlock prior to their practical use. One reason for this can be said to consist in that development of a compound having a large spontaneous polarization value Ps has been late.